Collimation device, radiology apparatus, test kit and method of testing a radiology apparatus

ABSTRACT

Collimation device of the type intended to direct an energy beam in a given direction and at a given solid angle, the collimation device being capable of being installed on output of an energy beam generating arrangement and of being connected to a control unit. The collimation device includes the ability for testing operation of the assembly formed by the energy beam generating arrangement the collimation device and the control unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of a priority under 35 USC 119 toFrench Patent Application No. 0007745 filed Jun. 16, 2000, the entirecontents of which are incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention concerns the field of electromagnetic radiationbeams used for different types of measurement and visualization. Theinvention is applicable notably to X-ray imaging or processing devices,for example, in the medical field.

A radiology apparatus generally comprises means for an X-ray emissionhaving equipped with an X-ray tube and a collimator, means for receivingthe X-ray emissions separated from the means for emission by a distancesufficient to place there an object that it is desired to study. Thecollimator serves to determine the solid angle of aperture of the X-raybeam. The X-ray beam can thus be limited to the surface of the receiver.The collimator can also serve to further reduce the solid angle of thebeam in order to limit it to a particular zone of interest of the objectthat is studied or processed, which makes it possible to prevent otherparts of the object from being subjected to X-rays. The collimator caninclude a diaphragm made according to the principle of the diaphragm ofa camera of articulated moving plane type. A diaphragm whose attenuatingmaterial consists of a deformable solid or of a fluid in a chamber isalso disclosed in FR-A-2,601,544.

In addition, a radiology apparatus further comprises an electroniccontrol unit for the X-ray tube, collimator, receiver (provided, forexample, with a scintillator), a high-voltage supply of the X-ray tube,etc.

Such an apparatus must be calibrated in order to attain a sufficientqualitative and quantitative precision of the structures observed on animage. The calibration is generally done by means of a phantom that isplaced at the object site on the path of the X-ray beam. A phantom is anobject separate from the apparatus and comprising parts opaque to X-raysarranged according to a geometry defined and known. An image of thephantom is acquired under the geometric conditions of an angle ofincidence that it is sought to be calibrated. The projections of thecharacteristic points are then recognized in the image. Eachcharacteristic point of the object is associated with its trace in theacquired image. The system of equation describing the projectionsupplying the image is inverted in the mathematical sense and the set ofparameters of the projection is finally obtained for the given vantagepoint. A phantom and method of calibration of an X-ray imaging system isdisclosed in FR-A-2,700,909 and EP-A-0,874,536.

BRIEF DESCRIPTION OF THE INVENTION

An embodiment of the present invention is directed to increasing theautomation of calibration of a system using electromagnetic radiation.An embodiment of the present invention proposes controlling thecalibration. An embodiment of the present invention proposes a phantomwhose risks of deterioration are reduced.

A collimation device, according to one embodiment of the invention, isof the type intended to direct an energy beam in a given direction andat a given solid angle. The collimation device is capable of beinginstalled on output of an energy beam generating means and of beingconnected to the control unit. The collimation device includes means fortesting operation of the assembly formed by the energy beam generatingmeans, the collimation device, the control device and a receiver. Themeans can be integrated with the device, for example, by being adjacentto the collimation elements. The means can be connected to the controlunit directly or indirectly. The collimation device advantageouslyincludes means for calibrating the operating parameters intended to beused by the control unit. In an embodiment of the invention, thecollimation device includes means for testing the operation of an X-raytube emitting the energy beam. The means are preferably capable of beingcommanded by a control unit. In an embodiment of the invention, themeans are capable of being remote-controlled by a computer installed onanother site.

In an embodiment of the invention, the means include a plurality of testtools with a position sensor of each tool. The collimation device caninclude a motion sensor of each tool. The progress or temporal change ofthe calibration can then be monitored.

A radiology apparatus, according to one aspect of the invention, meansfor emitting an energy beam means of reception for the energy beam, acontrol unit and a collimation device, such as described above.

A test kit, according to one embodiment of the invention, includes meansfor fastening to a collimation device, of the type designed to direct anenergy beam in a given direction and at a given solid angle and meansfor testing the operation of the collimation device means for emittingenergy beam and a control unit. The test kit can advantageously beequipped with means for communicating with the control unit. The testkit is therefore capable of being fastened to collimation device,notably, below the latter in the direction of propagation of the energybeam. The test kit can be fastened on a collimation device with littleor no structural modifications.

The invention also proposes a method for testing a radiology apparatus,in which the operation of the apparatus is tested by means of toolsforming part of a collimation device, the tools making it possible tofunctionally define the operation of the means for emitting an energybeam of the collimation device and of a receiver.

The invention is also directed to a computer program including means forproviding a program code for applying the steps of the above-mentionedmethod.

The invention likewise is directed to a storage medium capable of beingread by a device for reading the program code which are stored there inand which are capable of applying the steps of the abovementionedmethod.

The invention also makes possible a remote control of the quality ofoperation of an apparatus, notably of a radiology apparatus, by makingpossible a calibration remote-controlled from a maintenance center, forexample, with telecommunication through an Internet-type network, or anautomatic calibration at given time intervals or operating times, whileproviding for the possibility that a negative result of automaticcalibration might trip an alarm in a maintenance center which can alsobe remotely situated.

For that purpose, the collimation device may comprise: one or more leadplates for calibration of the X-ray tube that is done by emittingX-rays; one or more copper plates for calibration of the gain responseof the entire information processing system formed by the apparatus,which makes it possible to characterize, notably, the aging of the X-raytube; one or more aluminum plates for spectral characterization of theX-ray beam and dose measurement. Several aluminum plates will preferablybe provided to determine at what thickness of aluminum the dose isdivided by a given factor; one or more wires of radiation-absorbentmaterial; one or more grids of radiation-absorbent material; one or moreplates of radiation-absorbent material of thickness calibrated in stepsto make calibration of the image quality possible.

The persistence or kinetic blur due, for example, to the scintillator,which continues to emit an output signal when the input signal (X-rays)has been interrupted can be calibrated. The progress of presistence ismonitored by placing one or more test objects in the beam, automaticallycontrolling the speed and position of the test objects.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is illustrated by the attached drawingsin which:

FIG. 1 is a schematic view of a collimator;

FIGS. 2, 4, 6 and 7 are schematic views in perspective of test tools;

FIG. 3 is a schematic view of a test kit;

FIG. 5 is a schematic side view in elevation of the test tool of FIG. 4;

FIG. 8 is a diagram of steps of operation; and

FIG. 9 is a diagram of an architecture of a radiology apparatus.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, a collimation device 1 comprises a casing 2 provided with aninlet 3, an outlet 4 and a plurality of moving plates 5 to 12 opaque toX-rays. Plates 5 to 12 provide a collimation according to a rectangularformat of an X-ray beam 13 represented by a line of dots and dashesbeing propagated on an axis 14. The beam emanates from a focus 15situated in an X-ray tube not represented. Collimation makes it possibleto adapt the beam to the shapes of rectangular detectors of film,scintillator and CCD camera type, or solid state detectors, or organscrossed by the X-ray beam.

The collimation device 1 also includes an additional casing 16 placed incontact with the lower aperture 4 of casing 2 and also arranged to betransparent to X-rays. Inside casing 16, there is a disk 17rotary-mounted and driven by a motor 18, the rotation being detected bya sensor 19, for example, of optical type reading an optical coder, notrepresented, which can comprise a sequence of alternate light and darkzones arranged on the upper surface of the disk 17, close to itsperiphery, opposite the sensor 19.

An embodiment of the disk 17 is illustrated in FIG. 2. The disk 17comprises a plurality, for example seven, of circular zones 22 to 28.The diameter and the positioning of the circular zones 22 to 28 on thedisk 17 are such that the X-ray beam 13 illustrated in FIG. 1 presents adiameter slightly less than that of one of the circular zones 22 to 28,when it crosses one of the circular zones 22 to 28. Circular zone 22 isempty and is used in normal operation of a radiology apparatus, forexample, on taking an X-ray image of a patient. Circular zone 23 is analuminum plate of given thickness that allows testing of the variationof spectral quality due to aging of the X-ray tube, which makes itpossible to determine when it is advisable to change the tube in orderto avoid a shutdown of the radiology apparatus due to a malfunction. Theinformation on change of spectral quality can also be used forcalibration of the exposure parameters, such as high service voltage ofthe X-ray tube, service current, etc. Circular zone 24 comprises atwo-dimensional phantom such as a metal grid of given material andthickness. Circular zone 25 also comprises a phantom, for example, inthe form of a sheet with defined beveled edges. Those two phantoms makepossible an evaluation of image quality. Circular zone 26 comprises aplate of heavy metal, for example, 2 mm thickness of lead, which makesit possible to totally block the X-ray beam. Circular zone 27 comprisesa copper plate of given thickness, for example, 2 mm. Circular zone 28also comprises a copper plate of different thickness from circular zone27. Both circular zones 27 and 28 can be used for calibration of theX-ray dose without it being necessary to use a dosimeter.

A motor 18 for turning the disk 17 on instruction of the radiologyapparatus control unit 20, allows the different steps of calibration toproceed automatically. The intervention of an operator can be reduced tothe decision to initiate calibration. The operator can be located onsite or at a remote maintenance center connected by digital link to theradiology apparatus. Calibration can also be carried out automatically,for example, outside of normal working hours of the radiology apparatusand the necessary adjustments of the parameters of the radiologyapparatus can be made while being able to signal a fault requiringattention by means of a local alarm and/or to a remote maintenancecenter. A sensor 19, makes it possible to ascertain the position andpossibly the speed of rotation of the disk 17, is also connected to thecontrol unit 20 of the radiology apparatus.

As can be seen in FIG. 1, the control unit 20 is joined by a wireconnection 21 to the operation test means formed by the casing 16equipped with the disk 17, motor 18 and sensor 19. However, a wirelesslink or even a connection through casing 2 could also be provided. Thecontrol unit 20 can be dedicated to the operation test means, ordedicated to the collimation device 1, or can form a central controlunit of the radiology apparatus to which the collimation device 1 is apart. The control unit 20 includes at least one processor, at least onememory and at least one set of control instructions stored in memory andcapable of being executed by the processor.

Casing 16 and casing 2 can be interlocked, for example, by means ofscrews, not represented. Casings 2 and 16 can also be made in a singleunit. If casing 16 is separate from casing 2, it can be arranged to addan operation test means to the collimation device in the existingradiology apparatus, as shown in FIG. 3. In the latter case, the testmeans may be in the form of a test kit 29 having a general shape similarto the test means of the embodiment of FIG. 1 and provided, in addition,with two lugs 30 and 31, each provided with a screw 32, 33 capable ofcooperating in corresponding tapped holes of a collimation devicecasing.

In FIGS. 4 and 5, another test tool is illustrated, which can be placedinside a test means casing. The tool 34 has a cylindrical structure 35around which is placed a plurality of rectangular elements 36 comprisingthe same type of elements as the circular zones 22 to 28 illustrated inFIG. 2.

In the embodiment illustrated in FIG. 6, a test tool 37 comprises aplurality of square test elements 38 to 41, each hinged at an angle onan axis 42 ready to be placed on the path of an X-ray beam 43 that isrepresented here as a beam of parallel lines.

Of course, in both of the foregoing embodiments, the rotation of thetool 34 and of elements 38 to 41 of the tool 37 is motor-driven andmonitored by sensor(s) so that the control unit receives information onthe position and possibly the movement of these different elements.

In the embodiment illustrated in FIG. 7, the test tool 44 comprises twoblocks 45 and 46 made of a given radiation-absorption material and eachhaving a half-parallelepiped shape cut along a diagonal. The two blocks45 and 46 complement each other, in the sense that, on bringing them incontact, a rectangular parallelepiped is formed. The X-ray beam 43crosses the two blocks 45 and 46, the spacing of which determines thethickness of material crossed by the X-ray beam 43. The relativeposition of the blocks 45 and 46 is detected by sensor and is controlledby means of a motor.

Different steps used by a radiology apparatus control unit areillustrated by way of example in FIG. 8 by means of a routine stored inan internal memory of the control unit or outside the control unit.

At step 50, a routine of the control unit, which is dedicated tocalibration, verifies the time elapsed since the last calibration andcompares it with a predetermined ceiling. If the time elapsed is greaterthan the ceiling, one then proceeds to step 51; otherwise the program ishalted in order to be resumed later, for example, the next day at thesame time or after a few minutes of non-use of the radiology apparatus.At step 51, the program controls the movement of a test tool and, byconsidering the disk 17 of FIG. 2, the positioning of circular zone 23in place of circular zone 22, which is empty, on the path of the beam13. Then, a standard calibration is carried out with the circular zone23. At steps 52 to 56, the program controls the corresponding operationsfor circular zones 24 to 28.

At stage 57, the routine controls the movement of the disk 17, so thatcircular zone 22, which is empty, is placed on the path of the beam 13.If, in the course of one of steps 52 to 56, calibration reveals a faultwhich the control unit cannot remedy by itself, the program controls analarm stage 58 either on site, for example, on a screen of the radiologyapparatus, or at a remote maintenance center, the alarm beingadvantageously accompanied by a message relating to the nature of thefault, its seriousness, a down time of the radiology apparatus, etc.Otherwise, calibration is terminated and the time elapsed since the lastcalibration is reset at step 59.

In FIG. 9, the radiology apparatus comprises, in addition to the centralunit 20 and collimation device 1, an X-ray tube 60 integral with thecollimation device 1, a high-voltage generator 61 for powering the tube60, a receiver 62, provided, for example, with a scintillator and amatrix camera, and a monitor 63 provided with a screen 64 for thedisplay of X-ray images.

The present invention makes it possible to design tools for automatictesting of an electromagnetic ray imaging and processing apparatus. Thetest tools can come in the form of a kit that is added to an existingcollimator or can be integrated with a collimator. Remote image qualitycontrol can thus be carried out with diagnosis in real time andpreventive maintenance. The test tool rests permanently on the imagingapparatus and possesses a deactivated position in which the beam ofelectromagnetic rays does not encounter any obstacle. The image taken innormal operation of the imaging apparatus does not therefore undergo anyattenuation or diminution of quality.

It is important to know precisely the movement of a tool across the beamin order to be able to deduce therefrom an estimate of the remanence andto monitor the progress of remanence in the course of time, that is,aging of the receiver 62 and, notably, of the scintillator. For thatpurpose, a tool will be moved in a few milliseconds in the X-ray beamintermittently and at constant speed.

The radiology apparatus whose control unit is connected to the test toolis advantageously provided with a remote link, digital, for example, toa maintenance center, which makes it possible to perform a number ofmaintenance operations without the service call of a maintenanceoperator.

Other maintenance operations can be carried out with the service call ofa maintenance operator, who will have identified the component to bereplaced before his trip, which will also make it possible to reduce thenumber of trips.

The handling of a phantom separate from the apparatus becomessuperfluous, which reduces the risks of loss or deterioration of thephantom likely to distort the calibration.

Various modifications in structure and/or steps and/or function may bemade by one skilled in the art without departing from the scope andextent of the invention as recited in the claims.

1. A collimation device to direct an energy beam in a given directionand at a given solid angle, the collimation device capable of beinginstalled at an output of means for emission of an energy beam andcapable of being connected to a control unit, comprising: means fortesting operation of an assembly formed by the means for emission of anenergy beam and the collimation device and means for receiving theenergy beam; the means for testing comprising: means for providing aplurality of test tools; and means for sensing the position of each testtool.
 2. The collimation device according to claim 1 comprising meansfor calibrating operating parameters used by the control unit.
 3. Thecollimation device according to claim 1, wherein the means for testingcomprises means for testing the operation of an energy beam emissiontube.
 4. The collimation device according to claim 2, wherein the meansfor testing comprises means for testing the operation of an energy beamemission tube.
 5. The collimation device according to claim 3 whereinany one of the means for emission or the means for testing or the meansfor receiving are capable of being commanded by the control unit.
 6. Thecollimation device according to claim 3 wherein any one of the means foremission or the means for testing or the means for receiving are capableof being remote-controlled by a computer at site separate from the siteof the collimation device.
 7. The collimation device according to claim1 wherein the means for sensing is a motion sensor for each tool.
 8. Aradiology apparatus having: means for emission of an energy beam; meansfor reception of the energy beam; a control unit; and a collimationdevice, the collimation device comprising: means for testing operationof an assembly formed by the means for emission of an energy beam andthe collimation device and the means for reception of the energy beam;the control unit for providing instructions to the means for testing;and the means for testing comprising; a plurality of test tools; and asensor for sensing the position of each test tool.
 9. A test kitcomprising: means for fastening the test kit to a collimation devicewhich directs an energy beam in a given direction and at a given solidangle; means for testing the operation of the collimation device; meansfor receiving an energy beam from the collimation device; a controlunit; and the means for testing comprising; a plurality of test toolswith a sensor of for sensing the position of each test tool.
 10. Thecollimation device of claim 1 wherein the means for testing comprises: aplurality of elements to test the operating characteristic or parametersof the means for emission or the means for receiving.
 11. The collimatordevice of claim 10 wherein the plurality of elements comprise means fortesting spectral quality.
 12. The collimator device of claim 10 whereinthe plurality of elements comprise means for calibrating radiation dose.13. The collimator device of claim 10 wherein the plurality of elementscomprise means for evaluating image quality.
 14. The collimation deviceof claim 10 wherein the plurality of elements comprise means forblocking the energy beam.
 15. The collimation device of claim 10 whereinthe plurality of elements comprise means for permitting the energy beamto be transmitted through at least one of the elements.
 16. Thecollimation device of claim 10 wherein the plurality of elementscomprise means for providing a phantom for evaluating image quality. 17.The collimation device of claim 1 wherein the means for testing isintegrated with the collimation device.
 18. The collimation device ofclaim 1 wherein the means for testing is separable from the collimationdevice.
 19. The collimation device of claim 1 wherein the means fortesting comprises means for securing the means for testing to thedevice.
 20. The collimation device of claim 1 wherein the control unitis connected to the device by a wire.
 21. The collimation device ofclaim 1 wherein the control unit is not connected to the device by awire.
 22. The collimation device of claim 1 wherein the means fortesting comprises: a disk having a plurality of zones, each zonecomprising a test tool.
 23. The collimation device of claim 22 whereinthe plurality of zones comprises at least seven test tools.
 24. Thecollimation device of claim 11 wherein the means for testing spectralquality comprises: a metal plate of a given thickness.
 25. Thecollimation device of claim 12 wherein the means for calibratingradiation dose comprises: at least two metal plates of differentthicknesses.
 26. The collimation device of claim 13 wherein the meansfor evaluating image quality comprises two phantoms of differingcharacteristics.
 27. The collimation device of claim 14 wherein themeans for blocking comprises a plate of a heavy metal.
 28. Thecollimation device of claim 15 wherein the means for permitting theenergy beam to be transmitted comprises the absence of a test toolelement.
 29. The collimation device of claim 10 wherein the means fortesting comprises: a rotatable cylinder having on the periphery thereofthe plurality of elements.
 30. The collimation device of claim 10wherein the plurality of test elements comprises: a plurality of plateshinged at a common pivot and selectively inserted in the energy beam.31. The collimation device of claim 10 wherein the plurality of testelements comprises a pair of adjacent one-half parallelepiped blocks,the blocks being of a radiation absorbing material.
 32. The test kit ofclaim 5 wherein the means for testing comprises: a plurality of elementsto test the an operating characteristic or parameters of the an emissionof the energy beam.
 33. The test kit of claim 5 wherein the plurality oftest tools comprise means for testing spectral quality.
 34. The test kitof claim 5 wherein the plurality of test tools comprise means forcalibrating radiation dose.
 35. The test kit of claim 5 herein theplurality of test tools comprise means for evaluating image quality. 36.The test kit of claim 5 wherein the plurality of elements test toolscomprise means for blocking the energy beam.
 37. The test kit of claim 5wherein the plurality of elements test tools comprise means forpermitting the energy beam to be transmitted through at least one of theelements.
 38. The test kit of claim 5 wherein the plurality of elementstest tools comprise means for providing a phantom for evaluating imagequality.
 39. The test kit of claim 5 wherein the control unit isconnected to the device by a wire.
 40. The test kit of claim 5 whereinthe control unit is not connected to the device by a wire.
 41. The testkit of claim 5 wherein the means for testing comprises: a disk having aplurality of zones, each zone comprising a test tool.
 42. The test kitof claim 41 wherein the plurality of zones comprises at least seven testtools.
 43. The test kit of claim 34 wherein the means for testingspectral quality comprises: a metal plate of a given thickness.
 44. Thetest kit of claim 34 wherein the means for calibrating radiation dosecomprises: at least two metal plates of different thicknesses.
 45. Thetest kit of claim 35 wherein the means for evaluating image qualitycomprises two phantoms of differing characteristics.
 46. The test kit ofclaim 36 wherein the means for blocking comprises a plate of a heavymetal.
 47. The test kit of claim 37 wherein the means for permitting theenergy beam to be transmitted comprises the absence of a test toolelement.
 48. The test kit of claim 32 wherein the means for testingcomprises: a rotatable cylinder having on the periphery thereof theplurality of elements.
 49. The test kit of claim 32 wherein theplurality of test elements comprises: a plurality of plates hinged at acommon pivot and selectively inserted in the energy beam.
 50. The testkit of claim 32 wherein the plurality of test elements comprises a pairof adjacent one-half parallelepiped blocks, the blocks being of aradiation absorbing material.